Herbicide, capsulated

In this book we introduce major techniques used in designing and developing, roughly in the sequence in which they will be used. We show how techniques have been used (or could have been used) in a variety of products a laundry detergent, insulated windows, toothpaste, anti-fouling paint, an insulin injector, a powder coating, a box of matches, herbicide capsules, foamed snacks, a pharmaceutical tablet. Rockwool insulation, a ballpoint and a methanol catalyst. The authors have been involved in the development of several of these products. 

The encapsulation of herbicides has received much attention. Encapsulated alachlor is a high volume herbicide product generally sold as a Hquid formulation, although a dry granule version is also available. The capsules, produced by interfacial polymeri2ation (11), are reported to be spherical with a diameter of 2—15 p.m (75). Two thiocarbamate herbicides, EPTC and vemolate [1929-77-7], were encapsulated by interfacial polymeri2ation because they are volatile compounds. When appHed in unencapsulated form, they must be incorporated in the soil within two hours in order to provide effective weed control. When appHed as a microencapsulated formulation, the rate of volatili2ation is lower and soil incorporation can be delayed 24 hours (76). 

The lens is an avascular transparent tissue surrounded by an elastic, collagenous capsule. Disturbances in the normal metabolism of the lens and rupture of the lens alter its optical characteristics, and may cause cataract, i.e., reduced transparency of the lens. For example exposure to a herbicide, 2,4-dichlorophenol, may cause cataract. 

During a hastily set up brainstorming session, we come up with an idea to beat them (Figure 11-2). We are to develop a herbicide that only releases active material when it is required during wet weather. This will be better for the roses, for the environment (the garden) and possibly for the gardener. We assume without further work that it will be better for our sales. The idea is to use a capsule made of a biopolymer such as gelatine. Such... 

The active material in our herbicide is a liquid that does not mix with water. It can be dispersed as droplets with a mixer - in our case the droplets have to be about 0.3 mm in diameter (Figure 11-7). If you then let a polymer-rich phase form by coacervation, the polymer spontaneously wets the drop surface. It forms a liquid polymer layer around the drop. Cross-linking the polymer gives a solid capsule. 

Powder Coating Capsulated Herbicide Chewing Gum Bread... 

Formation of microcapsules by in situ interfacial polymerization (where the monomers are entirely in the oil phase of the capsule core) yields microcapsules with a high core-to-wall ratio and a bilayer wall with an outer layer (about 0.05 urn) and an inner reinforcing spongy layer (0.5 fim). This method has been used to encapsulate a range of insecticides, pheromones, and herbicides, many of which have been available commercially (37). The capsule size may be varied from submicrometer to 100 /um diameter and the permeability selected for rapid or slow release of... 

Experimental toxicity trials showed cattle and sheep to be less tolerant than rodents to oral intake of triazines and other herbicides (Milhaud and Pilault 1977). One dose of 500 mg/kg simazine had a lethal effect in sheep (Hapke 1986). Toxic effects cumulated with successive doses 31 daily doses of 50 mg/kg or 14 doses of 100 mg/kg were lethal to sheep. Corresponding results were obtained with atrazine and prometone (Palmer and Radeleff 1969). Signs of severe poisoning were weakness, ataxia, and posterior paresis or paralysis, appearing with a lag of as much as 3 weeks. Substances were administered by capsules or drench. 

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